Bruce writes:

> Continuing my campaign to rid the net of nits, I'll point out that the
>  speed of light was first measured about 325 years ago, when Danish
>  astronomer Claus Roemer used the difference between the predicted and
>  observed transit times of Jupiter's moons to compute the time required
>  for light to cross from Jupiter to Earth.

Let me net your nit -- and double it (besides, what good is hand-to-hand nit-
picking without a little blood on the floor? :-).

I know of no Danish astronomer named Claus Roemer, but the Danish astronomer
Ole Romer did invent the transit circle in 1689. A transit circle is an
instrument designed to determine accurately the exact time at which a
celestial object transits an observer's celestial meridian.

Because the referenced years are nearly identical (1998 - 325 = 1673), I
suspect that we're talking about the same person.

But more than that, any "speed of light" measurement derived from such a crude
measurement would be good only the first decimal place, if that. While
virtually no one believed that the speed of light was infinite -- and thus
truly immeasurable -- measuring the speed of light accurately clearly proved
to be a significant challenge.

The first person to take up the challenge of measuring the speed of light
seriously was A. A. Michelson. All of the history of Michelson that I'm to
recount is from memory, so it too may have one or two hidden nits in it -- but
I did tell this story often when I taught introductory and advanced
engineering classes on semiconductor physics, so at least the nits are well
aged and honorable.

The highlights of Michelson's story that I particularly like were that,
although he was born in Germany, he was raised as a young man in an apartment
above his father's store in Virginia City, Nevada -- as wild an old west town
as you'll ever find. That, btw, is the same town that the 1960's TV show,
"Bonanza," was based on -- and one of the episodes of Bonanza featured
Michelson as a young man.

Michelson's first scientific paper was entitled something like "On methods of
measuring the speed of light" (I'm deeply paraphrasing here). Of interest, his
last scientific paper, after a long and fruitful career, had exactly the same
title. There's a lot to be said for a life lived with symmetry.

Michelson eventually came to teach at the US Naval Academy -- and the Academy
still proudly mentions this fact often. However, Michelson couldn't stand the
regimentation that went along with the Navy and they parted company rather
bitterly.

Eventually, after 50 years of trying to constantly get a better sense of the
speed of light, the first truly definitive measurements were made in 1926-27
using a Michelson interferometer, bouncing light from Mt. San Antonio to Mt.
Wilson, near Los Angeles. The road that the US Geodetic Survey put to very
accurately measure the distance between the two mirrors is still there and is
still called Baseline Road.

Wirt Atmar